Perfluoroelastomer articles have achieved outstanding commercial success and are used in a wide variety of applications in which severe environments are encountered, in particular those end uses where exposure to high temperatures and aggressive chemicals occurs. For example, these articles are often used in seals for aircraft engines, in oil-well drilling devices, and in sealing elements for industrial equipment that operates at high temperatures.
The outstanding properties of perfluoroelastomer articles are largely attributable to the stability and inertness of the copolymerized perfluorinated monomer units that make up the major portion of the polymer backbones in these articles. Such monomers include tetrafluoroethylene and perfluoro(alkyl vinyl) ethers. In order to develop elastomeric properties fully, perfluoroelastomer polymers are cured, i.e. crosslinked. To this end, a small percentage of cure site monomer is copolymerized with the perfluorinated monomer units. Cure site monomers containing at least one nitrite group, for example perfluoro-8-cyano-5-methyl-3,6-dioxa-1-octene, are especially preferred. Such compositions are described in U.S. Pat. Nos. 4,281,092; 4,394,489; 5,789,489; and 5,789,509.
Perfluoroelastomer articles that are employed in oil-well drilling devices can be damaged by explosive decompression when the pressure present in deep wells is suddenly released. Cured elastomer articles typically contain small flaws (e.g. voids or regions of low crosslink density). In the high pressure environment experienced by perfluoroelastomer articles employed in oil-well drilling, gasses and other fluids may enter these flaws and reach equilibrium. If the drilling equipment is then depressurized too quickly, expulsion of the gasses and other fluids from the flaws can damage the elastomer articles, causing blisters, ruptures and fractures within the articles and on their surfaces.
Current trends in the Oil and Gas Industry are toward high pressure/high temperature (HPHT) applications which, in addition to resistance to explosive decompression, requires excellent thermal and chemical resistance.
Increasing the hardness of a perfluoroelastomer article by incorporating high levels of fillers can improve the article's resistance to explosive decompression. However, such high hardness articles may be too hard to seal well in high pressure environments.
It would be an improvement to have cured perfluoroelastomer elastomer articles that are both resistant to explosive decompression and which maintain the sealing properties of less hard elastomer articles.